We propose to measure in rats the effects of purified dietary fiber components and fibrous foods on intestinal transit time, intestinal microbiology, fecal enzymology and the absorption and utilization rate of vitamin B12, folacin, zinc, calcium and iron; we will also study the mechanisms of such effects. The test fibers will at least include the following: cellulose, pectin, alginic acid (a gum) and xylan (a hemicellulose). Wheat bran and a legume will also be investigated as examples of fibrous foods. Fibernutrient interactions will be examined in vitro under simulated gastrointestinal conditions and in vivo in germ-free rats and conventional controls. Radioactive isotopes of the nutrients under study will be used to quantify the effect of fiber on micronutrient absorption and utilization rate in vivo. Use of germ-free and conventional rats will allow us to determine if dietary fiber components act by way of providing substrate for intestinal growth and/or metabolism, or by way of their physical-chemical properties, or both. Food fiber is a mixture of non-digestible components. We believe that it is of primary importance to determine the metabolic and physiological effects particularly with respect to micronutrient availability of the separate fiber entities so that predictions of the action(s) of various fibrous foods can be made when the composition of food fibers is known.